Thread: scanf end console my application...help!

Hi everyones, I do not understand why it does that and i need help. My code end after typing the first number and doesn't go to the second input... thanks in advance.. i'm new to c programming.

my code:

Don't post images of code or output. Just post the text. Post code with code tags.

I don't know why it wouldn't be reading two numbers. That doesn't make sense.

Your test for overflow and underflow is wrong for multiple reasons.

The computation a + b converts a and b to ints before the addition ("integer promotions").

Also, it is not guaranteed that signed values will wrap around in that way. It is "implementation defined" and may even raise a signal (I believe gcc has a flag to make it raise SIGABRT).

Also, if you enter a value greater than SHRT_MAX or less than SHRT_MIN in the first place, it's undefined behaviour (all bets are off).

To be safe, you would read the input as a string and then use strtol to convert it to a long and eventually check if it's in the short range.

I won't go into all that, but here's a way to check for overflow/underflow:

Code:

#include <stdio.h>
#include <limits.h>

int main() {
    short a, b;

    printf("Enter two numbers between %d and %d, inclusive\n",
           SHRT_MIN, SHRT_MAX);
    scanf("%hd%hd", &a, &b);

    if (a > 0 && b > SHRT_MAX - a)
        printf("Overflow\n");
    else if (a < 0 && b < SHRT_MIN - a)
        printf("Underflow\n");
    else
        printf("Okay %d\n", a + b);

    return 0;
}

Very kind of you, thanks for the reply!

Originally Posted by kzzmzz

I dont know how did you compile it without error message

Obviously that's not the code he compiled since, as you say, it won't compile.

you then have

Code:

if ((a > 0) && (b > 0) && (a+b<0))

true true false

and this is not true it cant become true what ever you type for a and b.

You don't know what you're talking about. Obviously the OP was expecting the value to "wrap around" to a negative value if a and b were too large to be added together within a short. I gave the reasons why this is not a good thing to do.

Try this yourself:

Code:

#include <stdio.h>
#include <limits.h>

int main() {
    int a = INT_MAX, b = INT_MAX;
    if (a > 0 && b > 0 && a + b < 0)
        printf("What do you know?\n");
    return 0;
}

Although it probably "works" on your machine, it is not guaranteed to work by the C standard. The original question also had problems associated with using short ints.